Spinal Cord Anatomy and Ascending and Descending Pathways

Question 1

What do somatosensory afferents and motor efferents to skeletal muscle travel by?

Answer 1

Spinal cord

Question 2

Spinal cord function

Answer 2

Receives 1o afferent fibres from peripheral receptors
Sends motor axons to skeletal muscle
Communications between brain and periphery
Preganglionic neurons of SYM and some of PSYM

Question 3

How many spinal nerves does the spinal cord produce?

Answer 3

31

Question 4

What are the enlargements associated with?

Answer 4

Cervical = upper limb
Lumbar = lower limb

Question 5

What occurs at each segment?

Answer 5

Rootlets from dorsal and ventral produce ant and post rootlets
Passing through subarachnoid space until reach vertebral formina
Post root is enlarge by dorsal root ganglion
Fuse = mixed spinal nerve= ant and post rami

Question 6

What is the spinal cord continuous with?

Answer 6

Medulla below foramen magnum

Question 7

Tapered cone shape spinal cord terminates as?

Answer 7

Conus medularis

Question 8

What does the conus medularis continue as?

Answer 8

Filum terminale (thin CT) 
Anchored to dorsum of coccyx

Question 9

Where does the spinal cord end?

Answer 9

L1 (L2 at birth)

Question 10

Where is the dural spinal cord and what does it include?

Answer 10

Below L1

Dorsal and ventral roots of L2 and lower nerves of filum terminale

Question 11

What is the collection of roots of the filum terminale called?

Answer 11

Cauda equina

Question 12

Where does the dural sac end?

Answer 12

S2
Dorsal and ventral roots pass out of the sack, remain in dura and travel in spinal canal now in CSF of subarachnoid space

Question 13

How are the spinal cord meninges continuous with the cranial meninges?

Answer 13

Foramen magnum

Question 14

What is the spinal cord suspended by?

Answer 14

Denticulate ligament

Question 15

How is the denticulate ligament formed?

Answer 15

From pial and arachnoid tissue

Question 16

Dorsal and ventral roots in IVC and dura and arachnoid mater merge with

Answer 16

CT around the nerve

Question 17

Where is the white mater located on the spinal cord?

Answer 17

Outside

Question 18

Where is the grey mater located on the spinal cord?

Answer 18

Inner H

Question 19

What does the white mater consist of?

Answer 19

Longitudinal axons
Glial cells
Blood vessels

Question 20

What does the grey mater consist of?

Answer 20

Neuronal soma
Cell processes
Synapses
Glia
Blood vessels

Question 21

Where does the small central canal running the length of the spinal cord open and close?

Answer 21

Rostral - opens into 4th ventricle

Caudal - blind ending - medulla?

Question 22

What occurs if there is damage to the white mater?

Answer 22

No more communication below that level

Question 23

What occurs if there is damage to the grey mater?

Answer 23

Damage/paralysis in band that is damdaged

Question 24

Where is grey mater greatest?

Answer 24

Cervical and lumbar enlargements

Question 25

Where is white mater greatest?

Answer 25

Cervical levels and less at caudal levels

Question 26

Where is the lateral horn/intermediolateral cell group? | And what does it contain?

Answer 26

T1-L2 Preganglionic SYM neurons SYM outflow

Question 27

Where is the PSYM outflow?

Answer 27

Above and below SYM outflow

Question 28

How are rexed laminae defined?

Answer 28

Cell size Shape Density

Question 29

Lamina I

Answer 29

Lamina marginalis | large diameter afferents synapse here

Question 30

Lamina II

Answer 30

Substantia gelatinosa | Pain fibres here

Question 31

Lamina III

Answer 31

Part of substantia genlatinosa and nucleus proprius | Afferents

Question 32

Lamina IV

Answer 32

Part of nucleus proprius | dendrites of tract cells

Question 33

Lamina V and VI

Answer 33

``` Base of dorsal horn Proprioceptive afferents Motor and sensory Movement (important in) Tract cells = give rise to spinothalamic tract ```

Question 34

Lamina VII

Answer 34

Intermediate horn Clarke's column (T1-L2) Proprioceptive fibres synapse Intermediolateral column (T1-L2) = SYM preganglionic neurons

Question 35

Lamina VIII

Answer 35

Proprioceptive interneurons

Question 36

Lamina IX

Answer 36

Alpha and gamma motor neurons

Question 37

Lamina X

Answer 37

Dorsal and ventral grey commisures

Question 38

Where is the tract of Lissauer?

Answer 38

Overlying lamina I Thin layer of white matter Afferents (pain + temp) enter cord divide into ascending and descending branches before entering grey matter

Question 39

Arterial supply of spinal cord

Answer 39

Ant and 2 post longitudinal aa. = originate from vertebral aa. (run length of cord) Segemental aa. - from vertebral, deep, cervical, intercostal and lumbar aa. Radicular aa. - travel along dorsal and ventral roots

Question 40

What is the great anterior segmental medullary artery?

Answer 40

Large radial a T9-11 | Supplies much of lower spinal cord

Question 41

What does the anterior spinal artery supply?

Answer 41

2/3rd of the spinal cord (cross section)

Question 42

What do longitudinal veins drain to?

Answer 42

Cerebellar veins and cranial sinuses

Question 43

What do segmental veins drain to?

Answer 43

Local vertebral plexuses then thoracic/ abdominal/ intercostal veins

Question 44

What is the epidural space occupied by?

Answer 44

Adipose tissue between bone and dura | Used in epidural anaesthesia

Question 45

Dorsal column (ascending tract)

Answer 45

Cuneate nucleus and gracile nucleus Fine touch and conscious proprioception and vibration sense Cross in medulla (Crossing of fibres – decusation) Arm =CF Leg=GF, graceful Synapse in medulla but also in nucleus granculus=medial and nucleus cuneatus –lateral

Question 46

What is proprioception?

Answer 46

sense of the relative position of one's own parts of the body and strength of effort being employed in movement

Question 47

Proprioception in lower limb

Answer 47

Some via the DC system. Some ascends in the DC to thoracic/upper lumbar regions Synapses in Clarke’s column, Projects to the medulla in the dorsal spinocerebellar tract. Then rejoins medial lemniscal system to reach thalamus and cortex.

Question 48

Other name for Clarke's column

Answer 48

Nucleus dorsalis

Question 49

Spinothalamic tract (as. tract)

Answer 49

Pain, temp and deep pressure | Fibres cross segmentally

Question 50

Tracts cells in lamina V-VI give rise to?

Answer 50

Spinothalamic tract

Question 51

Primary somatosensory cortex and sensory cortical homunculus

Answer 51

Somatotopic organisation of neurons = mapped out Sensory fibres crossed midline Left side of body = right cortex

Question 52

Corticospinal tract (descending tract)

Answer 52

Control of precision and speed of skilled movements Ridges (pyramids) on ant surface of medulla = pyramidal tract 85% fibres cross at caudal medulla - decussation of pyramids Crossed fibres from Lat CST Uncrossed = ventral CST - cross segmentally

Question 53

CST fibres travel in?

Answer 53

Post limb of internal capsule

Question 54

Rubrospinal tract

Answer 54

Excitory control of tone of limb flexor muscles Originate in red nucleus of midbrain and decussate here In lat column in SC, lat to CST Ends in upper C spinal cord

Question 55

Tectospinal tract

Answer 55

Small tract, input from C O in sup colliculus (tectum) Mediate reflex movement due to visual stimuli

Question 56

Lateral Vestibulospinal Tract

Answer 56

Excitatory input to “antigravity” extensor muscles. O in the ipsilateral vestibular nuclei of pons and medulla (these in turn receive input from vestibular apparatus and cerebellum). Fibres do not cross

Question 57

Reticulospinal Tract

Answer 57

Reticular formation forms the central core of the brainstem - IMPORTANT Many nuclei and receives input from virtually all parts of the CNS. Influencing of voluntary movement. O in areas of the reticular formation in pons and medulla. Fibres originating in pons facilitate extensor movements and inhibit flexor movements, while those originating in the medulla do the opposite. Also, because some fibres extend to many spinal levels it is thought they may help coordinate movement involving upper and lower limbs.

Question 58

Motor system outside of pyramidal tract is the

Answer 58

Extrapyramidal system

Question 59

Brown – sequard syndrome

Answer 59

Hemisection of the spinal cord- numb to fine touch, loose pain and temp fibres on opposite side